The AML1/ETO(MTG8) and AML1/Evi-1 leukemia-associated chimeric oncoproteins accumulate PEBP2beta(CBFbeta) in the nucleus more efficiently than wild-type AML1.
AML1, a gene on chromosome 21 encoding a transcription factor, is disrupted in the (8;21)(q22;q22) and (3;21)(q26;q22) chromosomal translocations associated with myelogenous leukemias; as a result, chimeric proteins AML1/ETO(MTG8) and AML1/Evi-1 are generated, respectively. To clarify the roles of AML1/ETO(MTG8) and AML1/Evi-1 in leukemogenesis, we investigated subcellular localization of these chimeric proteins by immunofluorescence labeling and subcellular fractionation of COS-7 cells that express these chimeric proteins. AML1/ETO(MTG8) and AML1/Evi-1 are nuclear proteins, as is wild-type AML1. Polyomavirus enhancer binding protein (PEBP)2beta(core binding factor [CBF]beta), a heterodimerizing partner of AML1 that is located mainly in the cytoplasm, was translocated into the nucleus with dependence on the runt domain of AML1/ETO(MTG8) or AML1/Evi-1 when coexpressed with these chimeric proteins. When a comparable amount of wild-type AML1 or the chimeric proteins was coexpressed with PEBP2beta(CBFbeta), more of the cells expressing the chimeric proteins showed the nuclear accumulation of PEBP2beta(CBFbeta), as compared with the cells expressing wild-type AML1. We also showed that the chimeric proteins associate with PEBP2beta(CBFbeta) more effectively than wild-type AML1. These data suggest that the chimeric proteins are able to accumulate PEBP2beta(CBFbeta) in the nucleus more efficiently than wild-type AML1, probably because of the higher affinities of the chimeric proteins for PEBP2beta(CBFbeta) than that of wild-type AML1. These effects of the chimeric proteins on the cellular distribution of PEBP2beta(CBFbeta) possibly cause the dominant negative properties of the chimeric proteins over wild-type AML1 and account for one of the mechanisms through which these chimeric proteins contribute to leukemogenesis.
Tanaka
K
K
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
Tanaka
T
T
Kurokawa
M
M
Imai
Y
Y
Ogawa
S
S
Mitani
K
K
Yazaki
Y
Y
Hirai
H
H
D000818:Animals; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism*; D002471:Cell Transformation, Neoplastic; D002891:Chromosomes, Human, Pair 21; D050676:Core Binding Factor Alpha 2 Subunit; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D015870:Gene Expression; D006801:Humans; D007163:Immunosorbent Techniques; D007951:Leukemia, Myeloid / Q000235:genetics / Q000378:metabolism; D000074008:MDS1 and EVI1 Complex Locus Protein; D009363:Neoplasm Proteins / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D011519:Proto-Oncogenes; D000075142:RUNX1 Translocation Partner 1 Protein; D011993:Recombinant Fusion Proteins / Q000378:metabolism*; D050656:Transcription Factor AP-2; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014178:Translocation, Genetic
D050676:Core Binding Factor Alpha 2 Subunit; D004268:DNA-Binding Proteins; D000074008:MDS1 and EVI1 Complex Locus Protein; C063575:MECOM protein, human; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins; D000075142:RUNX1 Translocation Partner 1 Protein; C493728:RUNX1 protein, human; C082222:RUNX1T1 protein, human; D011993:Recombinant Fusion Proteins; D050656:Transcription Factor AP-2; D014157:Transcription Factors